P31 - Moonlight Matters: How Lunar Brightness Influences Mosquito Trap Catches in the Cayman Islands

Abstract: Light traps are widely used to monitor mosquito populations, providing critical information for control programmes. However, their effectiveness can be influenced by environmental factors such as moonlight. This study explored how variations in lunar illumination affect mosquito catches in Grand Cayman over more than two decades of continuous monitoring.

Daily moon illumination data from 2000–2024 were combined with mosquito light-trap records to examine patterns in catch rates across different lunar phases. The analysis revealed a clear and consistent trend: as moonlight increased, the number of mosquitoes collected declined. On average, each one-percent increase in moon illumination was associated with roughly a three-percent reduction in trap catch. This relationship held true throughout the 24-year dataset, suggesting that bright moon conditions regularly suppress trap performance.

These findings indicate that the brightness of the night sky can significantly influence light-trap results and may cause population densities to be underestimated during full-moon periods. Adjusting surveillance schedules or interpreting trap data with consideration of lunar phase could therefore improve the accuracy of mosquito population assessments and evaluations of control effectiveness.

By highlighting the predictable impact of moonlight on mosquito capture rates, this work underscores the importance of accounting for natural light cycles in long-term mosquito monitoring and in the planning of control operations.